US11497648B2ActiveUtilityA1
Advanced systems and methods for patient body temperature control
Est. expiryMay 12, 2037(~10.8 yrs left)· nominal 20-yr term from priority
A61F 7/12A61F 2007/0096A61F 7/0085A61F 2007/0054A61F 2007/126A61F 7/123A61F 2007/0093
52
PatentIndex Score
0
Cited by
26
References
21
Claims
Abstract
Devices, systems and methods for controlling the temperature of all or part of the body of a human or animal subject.
Claims
exact text as granted — not AI-modifiedWhat is claimed is:
1. A system for warming or cooling a subject to a target temperature, said system comprising:
a heat exchanger configured to exchange heat with the subject's flowing blood at a heat exchange location upstream or downstream of a target location;
a temperature sensor configured to sense a temperature of the subject's flowing blood at a temperature sensing location, which is upstream or downstream from the target location; and
a controller configured to:
receive one or more signals from the temperature sensor indicating the temperature of the subject's flowing blood being sensed at the temperature sensing location;
determine a heating or cooling power output of the heat exchanger, the heating or cooling power output being transferred to the subject from the heat exchanger;
determine a change in temperature of the temperature sensing location per unit of heating or cooling power output of the heat exchanger;
estimate the temperature at the target location, based on the heating or cooling power output of the heat exchanger, the change in temperature of the temperature sensing location per unit of heating or cooling power output of the heat exchanger, and the temperature sensed at the temperature sensing location; and
based on the estimated temperature at the target location, control the heat exchanger to warm or cool blood flowing through the heat exchange location as needed to result in warming or cooling of the target location to the target temperature.
2. A system according to claim 1 , wherein the target location is within a left ventricle of a heart of the subject, the heat exchange location is within an inferior vena cava or superior vena cava of the subject, and the temperature sensing location is in a vasculature of the subject downstream of the heat exchange location.
3. A system according to claim 2 , wherein the controller is configured to estimate a temperature within the left ventricle of the heart of the subject by estimating based on a temperature sensed in the inferior vena cava and at least in part on a change in the left ventricle temperature calculated as a function of the heating or cooling power output of the heat exchanger over time and a change in inferior vena cava temperature calculated as a function of the heating or cooling power output of the heat exchanger over time.
4. A system according to claim 3 , wherein the controller is configured to estimate the temperature within the left ventricle by estimating based additionally on a predetermined difference in blood temperature between the left ventricle and inferior vena cava.
5. A system of claim 1 , wherein the controller is configured to adjust the heating or cooling power output of the heat exchanger based on the estimated temperature at the target location.
6. A system according to claim 1 , wherein both the heat exchange location and the temperature sensing location are in an inferior vena cava (IVC) of the subject and the target location is in a left ventricle (LV) of a heart of the subject, and wherein the controller is programmed to estimate temperature at the target location within the left ventricle using a formula comprising:
TempLV=IVC+( K 2− K 1)·Power
Wherein:
TempLV is the estimated temperature at the target location within the left ventricle;
IVC is a current sensed temperature at the temperature sensing location;
K1 is a constant which represents a change in LV Temperature per Watt of the heating or cooling power output of the heat exchanger;
K2 is a constant which represents a change in IVC temperature per Watt of the heating or cooling power output; and
Power is the heating or cooling power output of the heat exchanger.
7. A system according to claim 6 , wherein K1 is calculated based on experimental or historical data.
8. A system according to claim 6 , wherein K1 is calculated using a formula comprising:
K 1= K 2·CK ratio
wherein CK ratio is a ratio of K1 to K2 determined based on experimental or historical data.
9. A system according to claim 6 , wherein the controller is pre-programmed with a value for K1.
10. A system according to claim 6 , further comprising a pump which pumps heat exchange fluid through the heat exchanger, wherein a pumping of said heat exchange fluid through the heat exchanger is stopped periodically or occasionally and K2 is calculated at each pump stop using a formula comprising:
IVC
At
X
sec
into
pump
stop
-
IVC
Before
pump
stop
Power
Before
pump
stop
.
11. A system according to claim 6 , wherein a heat exchange fluid is pumped through the heat exchanger and the heating or cooling power output is determined as:
Power (Watts)=(HE Fluid Temp OUT−HE Fluid Temp IN)·Flow Rate·CP
wherein:
HE Fluid Temp IN is a current measured temperature of heat exchange fluid flowing into the heat exchanger;
HE Fluid Temp OUT is a current measured temperature of heat exchange fluid flowing out of the heat exchanger;
Flow Rate is the measured or calculated flow rate of heat exchange fluid through the heat exchanger; and
CP is a specific heat capacity of the heat exchange fluid.
12. A system according to claim 6 , further comprising a pump which pumps heat exchange fluid through the heat exchanger, wherein a pumping of said heat exchange fluid through the heat exchanger is stopped periodically or occasionally and wherein the controller is programmed to perform steps comprising:
calculating and recording the heating or cooling power output before a pump stop;
recording IVC before said pump stop; effecting said pump stop;
recording IVC at x seconds into said pump stop;
calculating a new K2 value if the heating or cooling power output recorded before said pump stop is greater than a predetermined threshold value; and
applying the new K2 value, if calculated, for subsequent LV calculation.
13. A system according to claim 6 , further comprising a pump which pumps heat exchange fluid through the heat exchanger, wherein a pumping of said heat exchange fluid through the heat exchanger is stopped periodically or occasionally and wherein controller is programmed to perform steps comprising:
calculating and recording the heating or cooling power output before a pump stop;
recording IVC before said pump stop; effecting said pump stop;
recording IVC at x seconds into said pump stop;
if the heating or cooling power output recorded before said pump stop is greater than a predetermined threshold value, calculating new K1 and K2 values; and
applying the new K1 and K2 values, if calculated, for subsequent TempLV calculation.
14. A system according to claim 6 , further comprising a pump which pumps heat exchange fluid through the heat exchanger wherein the controller is programmed to perform steps comprising:
calculating and recording the heating or cooling power output before a pump stop of the pump;
recording IVC before said pump stop;
effecting said pump stop;
recording IVC at x seconds into said pump stop;
if the heating or cooling power output recorded before said pump stop is greater than a predetermined threshold value, calculating a new K2 value; and
if a new K2 value has been calculated, calculating a running average, median or filtered K2 value based on the new K2 value and one or more previous K2 values and, thereafter, using said running average, median or filtered K2 value for LV calculation.
15. A system according to claim 1 , wherein both the heat exchange location and the temperature sensing location are in an inferior vena cava (IVC) of the subject and the target location is in a left ventricle (LV) of a heart of the subject; and wherein the controller is programmed to estimate temperature at the target location within the left ventricle using a formula comprising:
TempLV=IVC+( K 2− K 1)·Power+ L,
wherein:
L is a constant which represents an expected change in the temperature of blood as it circulates through a right portion of a heart and lungs of the subject;
IVC is a current sensed temperature at the temperature sensing location;
K1 is a constant which represents a change in LV Temperature per Watt of the heating or cooling power output of the heat exchanger;
K2 is a constant which represents a change in IVC temperature per Watt of the heating or cooling power output; and
Power is the heating or cooling power output of the heat exchanger.
16. A system for warming or cooling a target location in a body of a subject to a target temperature, said system comprising:
a heat exchange catheter having a heat exchanger, said heat exchange catheter being insertable into a vasculature of the subject such that the heat exchanger is positioned at a heat exchange location within the vasculature of the subject;
a heater/cooler apparatus for alternately warming or cooling a heat exchange medium;
inflow and outflow conduits connecting the heater/cooler apparatus to the heat exchange catheter;
a pump for repeatedly circulating heat exchange fluid from the heater/cooler apparatus, through the inflow conduit, into the heat exchange catheter, through the heat exchanger, out of the heat exchange catheter, through the outflow conduit and back into the heater/cooler apparatus,
a temperature sensor that is positionable at a temperature sensing location within the subject's vasculature; and
a controller which receives signals from the temperature sensor indicating blood temperature at the temperature sensing location;
wherein the controller is configured to:
determine a heating or cooling power output of the heat exchanger, the heating or cooling power output being transferred to the subject from the heat exchanger;
determine a change in temperature of the temperature sensing location per unit of heating or cooling power output of the heat exchanger;
estimate the temperature at the target location based on the heating or cooling power output of the heat exchanger, the change in temperature of the temperature sensing location per unit of heating or cooling power output of the heat exchanger, and the temperature sensed at the temperature sensing location; and
control the temperature and/or a flow rate of the heat exchange fluid to cause the estimated temperature at the target location to rise or fall to the target temperature.
17. A system according to claim 16 , wherein both the heat exchange location and the temperature sensing location are in an inferior vena cava (IVC) of the subject and the target location is in a left ventricle (LV) of a heart of the subject, and wherein the controller is programmed to estimate a temperature at the target location within the left ventricle using a formula comprising:
TempLV=IVC+( K 2− K 1)·Power
wherein:
TempLV is the estimated temperature at the target location within the left ventricle;
IVC is a sensed temperature at the temperature sensing location;
K1 is a constant which represents a change in LV Temperature per Watt of the heating or cooling power output of the heat exchanger;
K2 is a constant which represents a change in IVC temperature per Watt the heating or cooling power output; and
Power is the heating or cooling power output of the heat exchanger.
18. A system according to claim 17 , wherein K1 is calculated using a formula comprising:
K 1= K 2·CK ratio
wherein CK ratio is a ratio of K1 to K2 determined based on experimental or historical data.
19. A system according to claim 17 , further comprising a pump which pumps heat exchange fluid through the heat exchanger, wherein a pumping of said heat exchange fluid through the heat exchanger is stopped periodically or occasionally and K2 is calculated at each pump stop using a formula comprising:
IVC
At
X
sec
into
pump
stop
-
IVC
Before
pump
stop
Power
Before
pump
stop
.
20. A system according to claim 17 , wherein Power is determined as:
Power (Watts)=(HE Fluid Temp OUT−HE Fluid Temp IN)·Flow Rate·CP
HE Fluid Temp IN is a current measured temperature of heat exchange fluid flowing into the heat exchanger;
HE Fluid Temp OUT is the current measured temperature of heat exchange fluid flowing out of the heat exchanger;
Flow Rate is the measured or calculated flow rate of heat exchange fluid through the heat exchanger; and
CP is a specific heat capacity of the heat exchange fluid.
21. A system according to claim 16 , wherein both the heat exchange location and the temperature sensing location are in an inferior vena cava of the subject and the target location is in left ventricle of a heart the subject, and wherein the controller is programmed to estimate temperature at the target location within the left ventricle using a formula comprising:
TempLV=IVC+( K 2− K 1)·Power+ L,
wherein:
L is a constant which represents an expected change in the blood temperature of blood that circulates through a right portion of the heart and lungs;
IVC is a current sensed temperature at the temperature sensing location;
K1 is a constant which represents a change in LV Temperature per Watt of the heating or cooling power output of the heat exchanger;
K2 is a constant which represents a change in IVC temperature per Watt of the heating or cooling power output; and
Power is the heating or cooling power output of the heat exchanger.Cited by (0)
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